Recently, printing systems are becoming popular in which client PCs (Personal Computers) are connected to a printing apparatus via a network and share the printing apparatus. When the users of the client PCs use the printing apparatus in this printing system, the users often stay away from the printing apparatus at the start of printing, and printed materials may attract the eye of a third party, losing confidentiality.
Under such a circumstance, there is proposed a printing system which takes a measure to protect a printed material from the eye of a third party (see, e.g., prior art reference 1: Japanese Patent Laid-Open No. 11-212744). In prior art reference 1, at the start of printing, the user inputs, e.g., a personal identification number or password into a client PC, and the client PC issues a print job with the personal identification number or password to a printing apparatus. Upon reception of the print job with the personal identification number or password, the printing apparatus temporarily stores it in a storage such as a memory or hard disk in the printing apparatus. The user comes to the printing apparatus and inputs his personal identification number or password from the panel of the main body, and then the printing apparatus starts printing.
Printing starts while the user is in front of the printing apparatus, and his printed material can be protected from the eye of a third party.
In order to start printing while the user is in front of the printing apparatus, a target print job must be specified. In general, a method of selecting a desired job by the user from a job list displayed on the screen of the printing apparatus, inputting his password, and then starting printing is adopted. In order to improve user's convenience, there is also proposed a method using an ID card instead of prompting the user to select a job or input his password (see, e.g., prior art reference 2: Japanese Patent Laid-Open No. 11-150559).
In prior art reference 2, ID information registered in an ID card is used as a personal identification number or password. When the ID card is inserted into a printing apparatus, the printing apparatus reads out the ID information, finds out a job which coincides with the readout ID information, and starts printing.
However, a printed material may be illicitly acquired by monitoring print jobs flowing through a network, copying a print job, and separately transmitting the copied print job to a printing apparatus. A printed material may also be illicitly acquired by copying data itself stored in a printing apparatus and separately transmitting the data to a printing apparatus.
To prevent this, there is proposed a system which encrypts print jobs flowing through a network and jobs stored in a printing apparatus (see, e.g., prior art reference 3: Japanese Patent Laid-Open No. 09-134264).
When a new printing system which encrypts data between a client PC and a printer is to be built, the client and printer environments are also renewed. To the contrary, to introduce an encryption printing function into a constructed printing environment, the encryption function must be provided to a print data generation unit having no encryption function so as to expand the existing printing environment, and the decryption function must be provided to a printing apparatus having no decryption function. The encryption printing system cannot be provided without greatly changing a conventional system configuration.